Superchargers in general provide a means for introducing air for combustion into the cylinder of an internal combustion (i/c) engine at a pressure in excess of that attainable by natural aspiration. Superchargers may be broadly defined as an air pump or blower in the intake system of an internal combustion engine used to increase the weight of air charge and consequent power output from a given engine size. These are broad definitional descriptions of a supercharger action and its relation to an internal combustion engine. With regard to an internal combustion engine a supercharger is provided to increase boost pressure, especially in aircraft i/c engines. Such boost pressure obtained by supercharging implies a manifold pressure greater than the ambient at atmospheric pressure, (cf. McGraw-Hill Dictionary of Scientific and Technical Terms; McGraw-Hill, Inc., 1974, New York, N.Y. p. 180). Other such definitions refer to a volumetric increase in the air charge to an engine or compartment as from a blower or compressor.
Historically, such superchargers or blowers were provided on i/c engine aircraft to increase the engine horsepower at elevated altitudes to the noted horsepower at sea level, or such blowers were utilized on racing vehicles to increase speed. These superchargers have not found general acceptance in the automobile industry primarily for three reasons (a) cost, (b) added fuel consumption and (c) the increased power derived was not recognized as a need in view of the first two reasons. The current automotive trend toward smaller engines or diesel engines in the automotive industry has highlighted a need for added power at least under certain circumstances such as rapid acceleration during passing or while carrying heavier loads. The accomplishment of this added power requirement without increasing engine size or adversely affecting fuel economy or performance is being attained by means of fuel injection, turbocharging, or supercharging among other means. Although a horsepower gain of about one-third could be realized by utilizing superchargers or blowers the concomitant preignition problems from an increased air charge pressure and temperature required the use of higher octane, thus higher cost fuel. In a diesel engine the increased air content from the blower permits the engine to burn more fuel and thus produces a higher horsepower output without creating combustion problems. Such improvements allow decreased size and weight of diesel engines.